ASHRAE REFRIGERATION IP CH 6-2010 REFRIGERANT SYSTEM CHEMISTRY《制冷系统化学过程》.pdf

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1、6.1CHAPTER 6REFRIGERANT SYSTEM CHEMISTRYRefrigerants. 6.1Chemical Reactions. 6.4Compatibility of Materials 6.10Chemical Evaluation Techniques 6.12Sustainability. 6.13YSTEM chemistry deals with chemical reactions between re-Sfrigerants, lubricants, and construction materials of various sys-tem compon

2、ents (e.g., compressor, heat transfer coils, connectingtubing, expansion device). Higher temperatures or contaminantssuch as air, moisture, and unwashed process chemicals complicatechemical interaction between components. Phase changes occur inthe refrigeration cycle, and in particular the temperatu

3、re extremes ina cycle from the highest discharge line temperature after the com-pression to the lowest evaporating temperature are of importance tothe end user. This chapter covers the chemical aspects of refriger-ants and lubricants, and their effects on materials compatibility.Detailed information

4、 on halocarbon and ammonia refrigerants isprovided in Chapters 1 and 2, respectively. Contaminant control isdiscussed in Chapter 7, and lubricants are discussed in Chapter 12.More information on various refrigerants can be found in Chapters29 and 30 of the 2009 ASHRAE HandbookFundamentals.REFRIGERAN

5、TSEnvironmental AcceptabilityRefrigerants are going through a transition because of globalenvironmental issues such as ozone depletion and climate changeconcerns. Information on available refrigerants, including thermo-dynamic and environmental properties, can be found in Chapter 29in the 2009 ASHRA

6、E HandbookFundamentals. Natural refriger-ants, including CO2(R-744), hydrocarbons, and some new candi-dates such as HFO-1234yf, are of particular interest because of theirlow global warming potential (GWP). For details, see Chapter 29 ofthe 2009 ASHRAE HandbookFundamentals.Common chlorine-containing

7、 refrigerants contribute to deple-tion of the ozone layer. A materials ozone depletion potential(ODP) is a measure of its ability, compared to CFC-11, to destroystratospheric ozone.Halocarbon refrigerants also can contribute to global warmingand are considered greenhouse gases. The global warming po

8、ten-tial (GWP) of a greenhouse gas is an index describing its ability,compared to CO2(which has a very long atmospheric lifespan), totrap radiant energy. The GWP, therefore, is connected to a particulartime scale (e.g., 100 or 500 years). For regulatory purposes, theconvention is to use the 100-year

9、 integrated time horizon (ITH).Appliances using a given refrigerant also consume energy, whichindirectly produces CO2emissions that contribute to global warm-ing; this indirect effect is frequently much larger than the refriger-ants direct effect. An appliances total equivalent warmingimpact (TEWI)

10、is based on the refrigerants direct warming poten-tial and indirect effect of the appliances energy use The life cycleclimate performance (LCCP), which includes the TEWI as well ascradle-to-grave considerations such as the climate change effect ofmanufacturing the refrigerant, transportation-related

11、 energy, andend-of-life disposal, is becoming more prevalent.Environmentally preferred refrigerants (1) have low or zeroODP, (2) provide good system efficiency, and (3) have low GWP orTEWI values. Hydrogen-containing compounds such as the hydro-chlorofluorocarbon HCFC-22 or the hydrofluorocarbon HFC

12、-134ahave shorter atmospheric lifetimes than chlorofluorocarbons(CFCs) because they are largely destroyed in the lower atmosphereby reactions with OH radicals, resulting in lower ODP and GWPvalues.Tables 1 and 2 show boiling points, atmospheric lifetimes, ODPs,GWPs, and flammabilities of new refrige

13、rants and the refrigerantsbeing replaced. ODP values were established through the MontrealProtocol and are unlikely to change. ODP values calculated usingthe latest scientific information are sometimes lower but are notused for regulatory purposes. Because HFCs do not contain chlorineatoms, their OD

14、P values are essentially zero (Ravishankara et al.1994).GWP values were established as a reference point using Inter-governmental Panel on Climate Change (IPCC 1995) assessmentvalues, as shown in Table 1, and are the official numbers used forreporting and compliance purposes to meet requirements of

15、theUnited Nations Framework Convention on Climate Change(UNFCCC) and Kyoto Protocol. However, lifetimes and GWPshave since been reviewed (IPCC 2001) and are shown in Table 2,representing the most recent published values based on an updatedassessment of the science. These values are subject to review

16、 andmay change with future reassessments, but are currently not used forregulatory compliance purposes. Table 3 shows bubble points andcalculated ODPs and GWPs for refrigerant blends, using the latestscientific assessment values.Compositional GroupsChlorofluorocarbons. CFC refrigerants such as R-12,

17、 R-11,R-114, and R-115 have been used extensively in the air-condition-ing and refrigeration industries. Because of their chlorine content,these materials have significant ODP values. The Montreal Proto-col, which governs the elimination of ozone-depleting substances,was strengthened at the London m

18、eeting in 1990 and confirmed atthe Copenhagen meeting in 1992. In accordance with this interna-tional agreement, production of CFCs in industrialized countrieswas totally phased out as of January 1, 1996. Production in devel-oping countries will be phased out in 2010, although many havealready made

19、considerable phaseout progress.Hydrochlorofluorocarbons. HCFC refrigerants such as R-22and R-123 have shorter atmospheric lifetimes (and lower ODP val-ues) than CFCs. Nevertheless, the Montreal Protocol limited devel-oped-country consumption of HCFCs beginning January 1, 1996,using a cap equal to 2.

20、8% of the 1989 ODP weighted consumption ofCFCs plus the 1989 ODP-weighted consumption of HCFCs. TheCAP was reduced by 35% by January 1, 2004, and will be reduced by65% on January 1, 2010; 90% by January 1, 2015; 99.5% by JanuaryThe preparation of this chapter is assigned to TC 3.2, Refrigerant Syste

21、mChemistry.6.2 2010 ASHRAE HandbookRefrigerationTable 1 Refrigerant Properties: Regulatory Compliance Values Used by Governments for UNFCCC Reporting and Kyoto Protocol ComplianceRefrigerant StructureBoiling PointaFAtmospheric Lifetime,bYears ODPcGWP,ITH 100-Year Flammable?E125 CHF2OCF343.6 165a15,3

22、00aNoE143 CHF2OCH2F85.8dYesE143a CF3OCH311.4 5.7a5400aYes11 CC13F 74.7 50 1 4600aNo12 CCl2F221.6 102 1 10,600aNo22 CHClF241.4 12.1 0.055 1900aNo23 CHF3115.8 264 11,700 No32 CH2F261.1 5.6 650 Yes113 CCl2FCClF2117.7 85 0.8 6000aNo114 CClF2CClF238.5 300 1 9800aNo115 CClF2CF338.0 1700 0.6 10,300aNo116 C

23、F3CF3108.8 10,000 11,400aNo123 CHCl2CF382.0 1.4 0.02 120aNo124 CHClFCF310.4 6.1 0.022 620aNo125 CHF2CF354.6 32.6 2800 No134a CH2FCF316.0 14.6 1300 No142b CClF2CH315.8 18.4 0.065 2300aYes143 CH2FCHF241.0 3.8 300 Yes143a CF3CH353.0 48.3 3800 Yes152a CHF2CH311.2 1.5 140 Yes218 CF3CF2CF333.9 2600a8600aN

24、o227ea CF3CHFCF33.9 36.5 2900 No236ea CF3CHFCHF243.7d10d9400aNo236fa CF3CH2CF329.5 209 6300 No245ca CHF2CF2CH2F 13.2 6.6 560 Yes245fa CF3CH2CHF259.2 8.8a820aNoaData from Calm and Hourahan (1999).bData from IPCC (1995).cData from Montreal Protocol (2003).dData from Chapter 5 of the 2006 ASHRAE Handbo

25、okRefrigeration.Table 2 Refrigerant Properties: Current IPCC Scientific Assessment ValuesRefrigerant StructureBoiling Point,FAtmospheric Lifetime,Years ODPGWP,ITHa100-Year Flammable?bE125 CHF2OCF343.6 165c14,900 NoE143 CHF2OCH2F85.1b 57 YesE143a CF3OCH311.4 5.7c750 Yes11 CHl3F 74.7 50 1 4600 No12 CC

26、l2F221.6 102 1 10,600 No22 CHClF241.4 12.1 0.055 1700 No23 CHF3115.8 264 12,000 No32 CH2F261.1 5.6 550 Yes113 CCl2FCF2Cl 117.7 85 0.8 6000 No114 CClF2CClF238.5 300 1 9800 No115 ClF2CF338.0 1700 0.6 7200 No116 CF3CF3108.8 10,000 11,900cNo123 CHCl2CF382.0 1.4 0.02 120 No124 CHClFCF310.4 6.1 0.022 620

27、No125 CHF2CF354.6 32.6 3400 No134a CH2FCF315.0 14.6 1300 No142b CH3CClF215.8 8.4 0.065 2400 Yes143 CH2FCHF241.0 3.8 330 Yes143a CH3CF353.0 48.3 4300 Yes152a CH3CHF211.2 1.5 120 Yes218 CF3CF2CF333.9 2600c8600cNo227ea CF3CHFCF33.9 36.5 3500 No236ea CF3CHFCHF243.7b10b1200 No236fa CF3CH2CF329.5 209 9400

28、 No245ca CHF2CF2CH2F 77.2 6.6 640 Yes245fa CF3CH2CHF259.2 8.8c950 NoaData from IPCC (2001).bData from ASHRAE Standard 34.cData from Calm and Hourahan (1999).Refrigerant System Chemistry 6.31, 2020; and total phaseout by January 1, 2030. From 2020 to 2030,HCFCs may only be used to service existing eq

29、uipment. Developingcountries must freeze HCFC ODP consumption at 2015 levels in2016, and completely phase out by January 1, 2040.In addition to the requirements of the Montreal Protocol, severalcountries have established their own regulations on HCFC phase-out. The United States met the Montreal Pro

30、tocols requirements bybanning consumption of R-141b (primarily used as a foam-blowingagent) on January 1, 2003, and phasing out HCFC-142b (primarilyfoams) and HCFC-22 for original equipment manufacturers(OEMs) beginning January 1, 2010. Production for service needs isallowed to continue. Production

31、and consumption of all otherHCFCs will be frozen on January 1, 2015. On January 1, 2020, pro-duction and consumption of R-22 and R-142b will be banned, fol-lowed by a ban on production and consumption of all other HCFCson January 1, 2030. As required by the Montreal Protocol, from2020 to 2030, virgi

32、n HCFCs may only be used to service existingequipment.The European Union accelerated the schedule to reduce HCFCconsumption by 15% on January 1, 2002, 55% on January 1, 2003,70% on January 1, 2004, 75% on January 1, 2008, with total phase-out on January 1, 2010. They also implemented several use res

33、tric-tions on HCFCs in air-conditioning and refrigeration equipment.U.S. and E.U. phaseout schedules allow continued, limited man-ufacture for developing-country needs or for export to other coun-tries where HCFCs are still legally used.Atmospheric studies (Calm et al. 1999; Wuebbles and Calm1997) s

34、uggest that phaseout of HCFC refrigerants, with low atmo-spheric lives, low ozone depletion potentials, low global warmingpotentials, low emissions, and high thermodynamic efficiencies,will result in an increase in global warming, but have a negligibleeffect on ozone depletion.HCFC-22 is the most wi

35、dely used hydrochlorofluorocarbon.R-410A is now the leading alternative for HCFC-22 for new equip-ment. R-407C is another HCFC-22 replacement and can be used inretrofits as well as in new equipment. HCFC-123 is used commer-cially in large chillers.Hydrofluorocarbons. These refrigerants contain no ch

36、lorineatoms, so their ODP is zero. HFC methanes, ethanes, and propaneshave been extensively considered for use in air conditioning andrefrigeration.Fluoromethanes. Mixtures that include R-32 (difluoromethane,CH2F2) are being promoted as a replacement for R-22 and R-502.For very-low-temperature appli

37、cations, R-23 (trifluoromethane,CHF3) has been used as a replacement for R-13 and R-503 (Atwoodand Zheng 1991).Fluoroethanes. Refrigerant 134a (CF3CH2F) of the fluoroethaneseries is used extensively as a direct replacement for R-12 and as areplacement for R-22 in higher-temperature applications. R-1

38、25and R-143a are used in azeotropes or zeotropic blends with R-32and/or R-134a as replacements for R-22 or R-502. R-152a is flam-mable and less efficient than R-134a in applications using suction-line heat exchangers (Sanvordenker 1992, but it is still beingconsidered for R-12 replacement. R-152a is

39、 also being consideredas a component, with R-22 and R-124, in zeotropic blends (Batemanet al. 1990; Bivens et al. 1989) that can be R-12 and R-500 alter-natives.Fluoropropanes. Desmarteau et al. (1991) identified a number offluoropropanes as potential refrigerants. R-245ca is being consid-ered as a

40、chlorine-free replacement for R-11. Evaluation by Doerret al. (1992) showed that R-245ca is stable and compatible with keycomponents of the hermetic system. However, Smith et al. (1993)demonstrated that R-245ca is slightly flammable in humid air atroom temperature. Keuper et al. (1996) investigated

41、R-245ca per-formance in a centrifugal chiller; they found that the refrigerantmight be useful in new equipment but posed some problems whenused as a retrofit for R-11 and R-123 machines. R-245fa is used asa chlorine-free replacement for R-11 and R-141b in foams, and isbeing considered as a refrigera

42、nt and commercialized in organicRankine-cycle and waste-heat-recovery systems. R-236fa has beencommercialized as a replacement for R-114 in naval centrifugalchillers.Fluoroethers. Booth (1937), Eiseman (1968), Kopko (1989),ONeill (1992), ONeill and Holdsworth (1990), and Wang et al.(1991) proposed t

43、hese compounds as refrigerants. Fluoroethers areusually more physiologically and chemically reactive than fluori-nated hydrocarbons. Fluorinated ethers have been used as anesthet-ics and convulsants (Krantz and Rudo 1966; Terrell et al. 1971a,1971b). Reactivity with glass is characteristic of some f

44、luoro-ethers (Doerr et al. 1993; Gross 1990; Simons et al. 1977). Misakiand Sekiya (1995, 1996) investigated 1-methoxyperfluoropropane(boiling point 93.6F) and 2-methoxyperfluoropropane (boilingpoint 84.9F) as potential low-pressure refrigerants. Bivens andMinor (1997) reviewed the status of fluoroe

45、thers currently underTable 3 Properties of Refrigerant BlendsaRefrig-erant CompositionBubblePoint,bF ODPcGWP,d 100-Year ITH401A (22/152a/124)/(53/13/34) 27.9 0.027 1100401B (22/152a/124)/(61/11/28) 30.8 0.028 1200401C (22/152a/124)/(33/15/52) 19.1 0.025 900402A (125/C3H8/22)/(60/2/38) 56.2 0.013 270

46、0402B (125/C3H8/22)/(38/2/60) 52.6 0.020 2300403A (C2H6/22/218)/(5/75/20) 54.0 0.026 3000403B (C2H6/22/218)/(5/56/39) 56.6 0.019 4300404A (125/143a/134a)/(44/52/4) 51.2 0 3800405A (22/152a/142b/C318)/(45/7/5.5/42.5)27.2 0.018 5200406A (22/600a/142b)/(55/4/41) 26.9 0.036 1900407A (32/125/134a)/(20/40

47、/40) 49.5 0 2000407B (32/125/134a)/(10/70/20) 52.2 0 2700407C (32/125/134a)/(23/25/52) 46.5 0 1700407D (32/125/134a)/(15/15/70) 39.1 0 1500407E (32/125/134a)/(25/15/60) 45.2 0 1400408A (125/143a/22)/(7/46/47) 48.3 0.016 3000409A (22/124/142b)/(60/25/15) 30.5 0.039 1500409B (22/124/142b)/(65/25/10) 3

48、2.1410A (32/125)/(50/50) 60.5 0 2000411A (R-1270/22/152a)/(1.5/87.5/11.0)39.1 0.030 1500411B (1270/22/152a)/(3/94/3) 42.9 0.032 1600412A (22/218/142b)/(70/5/25) 36.4 0.035 2200413A (218/134a/600a)/(9/88/3) 23.1 0 1900414A (22/124/600a/142b)/(51/28.5/4/16.5)29.2 0.032 1400414B (22/124/600a/142b)/(50/

49、39/1.5/9.5)27.2 0.031 1300415A (22/152a)/(82/18) 35.5 0.028 1400415B (22/152a)/(25/75) 17.9 0.009 500416A (134a/124/600)/(59/39.5/1.5) 10.1 0.010 1000417A (125/134a/600)/(46.6/50/3.4) 36.4 0.000 2200418A (290/22/152a)/(1.5/96/2.5) 42.2 0.33 1600500 (12/152a)/(73.8/26.2) 28.5 0.605 7900502 (22/115)/(48.8/51.2) 49.4 0.221 4500503 (23/13)/(40.1/59.9) 127.8 0.599 13,000507A (125/143a)/(50/50) 52.1 0 3900508A (23/116)/(39/61) 125.3 0 12,000508B (23/116)/(46/54) 124.6 0 12,000509A (22/218)/(44/56) 57.6 0.015 5600aData